I agree you have tricky and pacy wingers/inside forwards in abundance. If he does make additions at the back then the signings he has made up front do look like decent signings. I think all the indications are that he will move Theo in to the center this season. Especially with Bendtner leaving.
Two decent center backs who are proven in the prem and you have a really decent looking side. You wouldn't even need to sign a left back as Vermaelen can play there for the trickier games where a bit more defence is needed.
Just got to hope Wenger sees sense and signs both Samba and Cahill. He could almost definitely get the pair for 30 million. With the transfer fund he is supposed to have along with the 60-70 million he will get for Nasri and Cesc, is does make me wonder what he is waiting for.